1. Technical Field
The present invention relates to an inflator for inflating a vehicle occupant restraint, and particularly relates to an initiator in the inflator.
2. Description of the Prior Art
An inflator for an inflatable vehicle occupant restraint, such as an air bag, includes a housing containing a source of inflation fluid. The source of inflation fluid may include an ignitable gas generating material. The inflator is actuated when the vehicle experiences a condition that indicates the occurrence of a collision for which inflation of the air bag is desired. The collision-indicating condition may comprise, for example, the occurrence of a predetermined amount of vehicle deceleration.
The inflator for an air bag commonly includes an initiator having igniter material which ignites when the initiator is actuated. Ignition of the igniter material ignites the gas generating material. The gas generating material, when ignited, generates gas for inflating the air bag. The gas generating material typically ignites at a temperature of about 650.degree. F. or higher.
The inflator may on occasion be subjected to an abnormally high temperature. For example, if a vehicle is involved in a fire, the temperature in the vehicle adjacent the inflator may reach or exceed 650.degree. F. In such a situation, the gas generating material might be at a high enough temperature to ignite.
To avoid ignition of the gas generating material when the ambient vehicle temperature is excessively high, a quantity of auto ignition material is located within the inflator. The auto ignition material is specifically designed to ignite at a lower temperature than the temperature at which the gas generating material ignites. The typical auto ignition material ignites at around 350.degree. F. When the auto ignition material ignites, the gas generating material is ignited. Thus, the gas generating material is ignited when the ambient temperature is about 350.degree. F.